From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5534C433F5 for ; Mon, 21 Feb 2022 18:54:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233228AbiBUSy3 (ORCPT ); Mon, 21 Feb 2022 13:54:29 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:35452 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232490AbiBUSwk (ORCPT ); Mon, 21 Feb 2022 13:52:40 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 792EAE02F for ; Mon, 21 Feb 2022 10:51:51 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 09FE8614B7 for ; Mon, 21 Feb 2022 18:51:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DF29AC340E9; Mon, 21 Feb 2022 18:51:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1645469510; bh=xjLvyaGBZiq/b3k2zEg7s81j547b8CcmvjJSQsP0YyA=; h=Subject:To:From:Date:From; b=BocnByAZY8SVTHZ5WUdnxlvOMFuAKA5ubRyWPlTtHfSPrUOwLd09H/J9qvm5Wk+hg FvBdg8TzsbU14t/PlH/ahnMRsR8A0GIC6LLX5k+6A2CJeVL4JcfjuYibZKC5rYjff5 8kDz2iAatYWpSDywEO7mqQ0+nT8v62U559smx3vs= Subject: patch "sc16is7xx: Fix for incorrect data being transmitted" added to tty-linus To: phil@raspberrypi.com, gregkh@linuxfoundation.org, stable@vger.kernel.org From: Date: Mon, 21 Feb 2022 19:51:47 +0100 Message-ID: <164546950721338@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org This is a note to let you know that I've just added the patch titled sc16is7xx: Fix for incorrect data being transmitted to my tty git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git in the tty-linus branch. The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.) The patch will hopefully also be merged in Linus's tree for the next -rc kernel release. If you have any questions about this process, please let me know. >From eebb0f4e894f1e9577a56b337693d1051dd6ebfd Mon Sep 17 00:00:00 2001 From: Phil Elwell Date: Wed, 16 Feb 2022 16:08:02 +0000 Subject: sc16is7xx: Fix for incorrect data being transmitted UART drivers are meant to use the port spinlock within certain methods, to protect against reentrancy. The sc16is7xx driver does very little locking, presumably because when added it triggers "scheduling while atomic" errors. This is due to the use of mutexes within the regmap abstraction layer, and the mutex implementation's habit of sleeping the current thread while waiting for access. Unfortunately this lack of interlocking can lead to corruption of outbound data, which occurs when the buffer used for I2C transmission is used simultaneously by two threads - a work queue thread running sc16is7xx_tx_proc, and an IRQ thread in sc16is7xx_port_irq, both of which can call sc16is7xx_handle_tx. An earlier patch added efr_lock, a mutex that controls access to the EFR register. This mutex is already claimed in the IRQ handler, and all that is required is to claim the same mutex in sc16is7xx_tx_proc. See: https://github.com/raspberrypi/linux/issues/4885 Fixes: 6393ff1c4435 ("sc16is7xx: Use threaded IRQ") Cc: stable Signed-off-by: Phil Elwell Link: https://lore.kernel.org/r/20220216160802.1026013-1-phil@raspberrypi.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/sc16is7xx.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c index 64e7e6c8145f..38d1c0748533 100644 --- a/drivers/tty/serial/sc16is7xx.c +++ b/drivers/tty/serial/sc16is7xx.c @@ -734,12 +734,15 @@ static irqreturn_t sc16is7xx_irq(int irq, void *dev_id) static void sc16is7xx_tx_proc(struct kthread_work *ws) { struct uart_port *port = &(to_sc16is7xx_one(ws, tx_work)->port); + struct sc16is7xx_port *s = dev_get_drvdata(port->dev); if ((port->rs485.flags & SER_RS485_ENABLED) && (port->rs485.delay_rts_before_send > 0)) msleep(port->rs485.delay_rts_before_send); + mutex_lock(&s->efr_lock); sc16is7xx_handle_tx(port); + mutex_unlock(&s->efr_lock); } static void sc16is7xx_reconf_rs485(struct uart_port *port) -- 2.35.1